Rails is optional.

gemfiles/rack_2.gemfile

@@ -3,5 +3,6 @@
 source "https://rubygems.org"
 
 gem "rack", "~> 2.0"
+gem "railties"
 
 gemspec path: "../"

lib/rack/attack/cache.rb

@@ -6,8 +6,16 @@ class Cache
       attr_accessor :prefix
       attr_reader :last_epoch_time
 
-      def initialize
-        self.store = ::Rails.cache if defined?(::Rails.cache)
+      def self.default_store
+        if Object.const_defined?(:Rails) && Rails.singleton_class.method_defined?(:cache)
+          ::Rails.cache
+        else
+          ActiveSupport::Cache::MemoryStore.new
+        end
+      end
+
+      def initialize(store = self.class.default_store)
+        self.store = store
         @prefix = 'rack::attack'
       end
 

lib/rack/attack/railtie.rb

@@ -1,5 +1,11 @@
 # frozen_string_literal: true
 
+begin
+  require 'rails/railtie'
+rescue LoadError
+  return
+end
+
 module Rack
   class Attack
     class Railtie < ::Rails::Railtie

spec/acceptance/rails_middleware_spec.rb

@@ -2,7 +2,7 @@
 
 require_relative "../spec_helper"
 
-if defined?(Rails)
+if defined?(Rails::Application)
   describe "Middleware for Rails" do
     before do
       @app = Class.new(Rails::Application) do

spec/spec_helper.rb

@@ -5,13 +5,8 @@
 require "minitest/autorun"
 require "minitest/pride"
 require "rack/test"
-
-begin
-  require "rails"
-rescue LoadError
-  # Ignore.
-end
-
+# require "rails"
+require "active_support"
 require "rack/attack"
 
 if RUBY_ENGINE == "ruby"
@@ -33,11 +28,11 @@ def safe_require(name)
 class MiniTest::Spec
   include Rack::Test::Methods
 
-  if Object.const_defined?(:Rails)
-    before do
-      Rails.cache = nil
-    end
-  end
+  # if Object.const_defined?(:Rails)
+  #   before do
+  #     Rails.cache = nil
+  #   end
+  # end
 
   after do
     Rack::Attack.clear_configuration